1. Field of the Invention
This invention relates to a polar electronic component such as a solid electrolytic capacitor or diode which is designed for conveniently mounting to a circuit carrier by soldering. The present invention also relates to a structure for mounting such a polar electronic component to a circuit carrier such as a printed circuit board.
2. Description of the Related Art
A solid electrolytic capacitor, which is a typical example of polar electronic component, is known from Japanese Patent Publication No. 3(1991)-30977 for example. The capacitor disclosed in this Japanese document has such a structure as shown in FIGS. 9 to 11.
Specifically, the prior art capacitor comprises a capacitor element 11 which includes a capacitor chip 11a and an anode wire 11b projecting from the chip 11a. The capacitor also includes an anode lead 12 in electrical connection with the anode wire 11b, and a cathode lead 13 in electrical connection to the chip 11a. The capacitor element 11 together with part of the respective leads 12, 13 is enclosed in a resin package 14. The respective leads 12, 13 project out from opposite side faces 14a, 14b of the package 14 and are bent toward the underside of the resin package 14 for conveniently mounting, by soldering, to a surface of a printed circuit board A' (see FIG. 11) which carries an anode-side electrode pad A1' and a cathode-side electrode pad A2'.
According to the prior art arrangement, the resin package 14 together with the projecting portions of the respective leads 12, 13 is symmetric with respect to a central plane transverse to the anode wire 11b. Therefore, the polarity of the capacitor is not visually recognizable, so that the capacitor may be erroneously mounted on the circuit board A' in reverse polarity. The capacitor thus errouneously mounted generates a lot of heat, consequently damaging the capacitor and its related components in a critical way.
The polarity of the capacitor may be rendered visually recognizable by making the respective leads 12, 13 asymmetric with respect to their configurations and/or by forming a marking (not shown) on the upper face of the resin package 14 near one of the leads 12, 13. However, the asymmentry of the respective leads 12, 13 are not readily recognizable due to the small size of the capacitor, whereas the marking of the package 14 is not recognizable from below the capacitor. Thus, the slot or marking may still fail to provide an intended prevention of erroneous mounting of the capacitor.
Similar problems are also encountered in other surface mounting type polar electronic components such as a diode.